1. Field of the Invention
The present invention relates to an apparatus and a method for recording an image on recording media by illumination with light in a heated mode. More particularly, the invention relates to an apparatus and a method for recording an image on recording media which experiences transfer, color formation or a change in density at a specified site when the temperature of the specified site exceeds a threshold upon illumination with light.
2. Description of the Related Art
Conventionally, there is known a recording material consisting of a colorant sheet including a photothermal conversion layer, a colorant layer, etc and an image-receiving sheet including an image-receiving layer. The photothermal conversion layer is superposed on the image-receiving sheet. Applied light is converted to thermal energy in the photothermal conversion layer of the colorant sheet and the resulting thermal energy elevates the temperature of the colorant layer beyond a threshold, whereupon the colorant layer is urged against the image-receiving layer by ablation to form an image on the image-receiving layer (see JP-A-8-132654).
Since no image is formed unless the temperature of the colorant layer rises beyond a threshold, this type of recording materials has lower sensitivity to light than other conventional recording materials such as silver salt photosensitive materials. To compensate for this characteristic, an apparatus for recording an image on that type of recording materials equips a heating source in the form of a lamp such as a halogen lamp or an IR (infrared) lamp or a heater such as a Nichrome wire. There are some constitutions for such an apparatus for recording an image. A first example is a constitution that sub-heating light (i.e., the light emitted from the lamp as a heating source) and writing light (i.e., the recording light emitted from a recording light source via a half-mirror) are superposed and emitted (so-called xe2x80x9csimultaneous heatingxe2x80x9d and see JP-A-64-71771, etc.). A second example is a constitution that the recording material is preliminarily heated by application of the heat of radiation from the heater as a heating source (so-called xe2x80x9cpreheatingxe2x80x9d). A third example is that the sub-heating light is applied after the writing light to give additional heat (so-called xe2x80x9cpost-heatingxe2x80x9d).
FIGS. 15A to 15C exemplify applications of sub-heating light B for a single channel of writing light A. Preheating is possible if the sub-heating light B is applied in a position downstream to the writing light A in a recording direction of main scanning as shown in FIG. 15A. Simultaneously heating is possible if the writing light A and the sub-heating light B are applied in the same position as shown in FIG. 15B. Post-heating is possible if the sub-heating light B is applied in position upstream to the writing light A in a recording direction of main scanning as shown in FIG. 15C.
In order to get the desired effect with a limited amount of heat, the sub-heating light B is occasionally applied in a large width. In the case of preheating, the sub-heating light B extends parallel to the direction of movement of the recording material as shown in FIG. 16A or it extends perpendicular to the direction of movement of the recording material as shown in FIG. 16B. Otherwise, it may be inclined at a predetermined angle to the direction of movement of the recording material as shown in FIG. 16C.
The sub-heating light B may sometimes be applied in the presence of a one-dimensional array of writing light channels. In this case, preheating (or post-heating) can be accomplished by applying the sub-heating light B parallel to the writing light A channels that are arranged perpendicular to the direction of movement of the recording material as shown in FIG. 17A (which refers particularly to preheating). Preheating, simultaneous heating and post-heating can be accomplished by applying the sub-heating light B perpendicular to the direction of movement of the recording material in the presence of the writing light A channels that are arranged at a predetermined angle to the direction of movement of the recording material as shown in FIG. 17B. Preheating, simultaneous heating and post-heating can also be accomplished by applying the sub-heating light B at a predetermined angle to the direction of movement of the recording material in the presence of the writing light A channels that are arranged perpendicular to the direction of movement of the recording material as shown in FIG. 17C.
If the recording material is illuminated with the sub-heating light B that is applied either upstream or downstream in a recording direction of main scanning with respect to the writing light A that is to be or was applied to the recording material at a specified site, the temperature of the colorant layer at the specified site will rise beyond a threshold within a short time. Thus, the sensitivity of the recording material to the writing light A can be sufficiently increased to enable rapid recording of an image.
If recording is to be done by a plurality of writing light A channels which are positionally related to the sub-heating light B as shown in FIG. 17A, all channels of the writing light A are equally spaced from the sub-heating light B in the main scanning direction in which the recording material moves (rotates). However, the individual writing light A channels have different positional (distance) relationships if they are positionally related to the sub-heating light B as shown in FIGS. 17B and 17C.
If a plurality of writing light channels A are in a one-dimensional array, the positional relationship with the sub-heating light B shown in FIG. 17A, if not those shown in FIGS. 17B and 17C, is sufficient for each of the channels to be similarly adapted to have the same distance from the sub-heating light B. However, if one attempts to increase the recording density by narrowing the recording gap between adjacent channels of the writing light A as shown in FIG. 18, the approach illustrated in FIG. 17A cannot be taken since the channels are arranged in a two-dimensional pattern with all channels being inclined at a predetermined angle to the main scanning direction.
Hence, given the positional relationship between the writing light channels A and the sub-heating light B that is shown in FIG. 18, three heating modes, i.e., preheating, simultaneous heating and post-heating, occur in combination such that channel Nos. 1 and 5 of the writing light A are the farthest from the sub-heating light B. channel Nos. 2 and 4 of the writing light A are the second farthest, and channel No. 3 of the writing light A combines with the sub-heating light B to cause simultaneous heating. If the distance from the first to the fifth channel in the main scanning direction is short (100-200 xcexcm), the result of recording will not be seriously affected. However, if the distance is as great as 400 xcexcm, different recording channels have different recording characteristics and sensitivity, recording speed and even the quality of a recorded image may be deteriorated.
The present invention has been accomplished under these circumstances and has as an object providing a recording apparatus that allows the individual recording channels to maintain sufficiently uniform recording characteristics that a high-quality image can be recorded in high sensitivity and at high speed. Another object of the invention is to provide a recording method for implementing this apparatus.
The first object of the invention can be attained by a recording apparatus for recording on a recording medium in a heated mode. The recording medium being moved along a main scanning direction. The recording apparatus includes:
a first emitting portion emitting writing light for providing a plurality of recording spots on the recording medium, the recording spots being inclined at a predetermined angle with respect to the main scanning direction; and
a second emitting portion emitting sub-heating light for providing a heating spot on the recording medium,
wherein a distance between the heating spot and each of the recording spots is substantially constant in the main scanning direction.
In this recording apparatus, the heating spot from the second emitting portion is applied to the recording medium at equal distances in the main scanning direction from the recording spots applied by the first emitting portion so that the individual recording spots arranged over a wide area are subjected to sub-heating in equal duration (whether it is in a preheating, post-heating or simultaneous heating mode) to maintain uniform recording characteristics. This offers the advantage of eliminating recording spots of low sensitivity that are away from the heating spot, thereby enabling recording in high sensitivity at high speed.
Preferably, in the above recording apparatus, the first emitting portion provides rows of the recording spots being provided in an auxiliary scanning direction, and the second emitting portion provides as many heating spots as the rows of the recording spots. Further, a distance between each of the heating spots and each of the recording spots is substantially constant in the main scanning direction.
While the recording spots are arranged in a two-dimensional pattern, the heating spots are equally spaced from the columns of recording spots in the main scanning direction. In other words, as many heating spots as the columns of recording spots are arranged parallel to the latter. Therefore, if the recording medium is moved in the main scanning direction, the individual recording spots are heated under the same conditions by the heating spots and the two-dimensional array of the recording spots are heated uniformly by the minimum necessary number of heating spots.
Further preferably, in the above recording apparatus, the recording medium includes an image-receiving sheet and a colorant sheet. The image-receiving sheet is for being wound onto a recording drum of the recording apparatus. The image-receiving sheet includes an image-receiving layer. The colorant sheet is for being wound onto the image-receiving sheet so that a toner layer of the colorant sheet is superposed on the image-receiving layer of the image-receiving sheet in intimate contact with each other.
In this recording apparatus, if the colorant sheet superposed on the image-receiving sheet in intimate contact with each other is illuminated with the writing light and the sub-heating light, the energy of the applied light is converted to thermal energy in a photothermal conversion layer in the colorant sheet, causing the temperature of the areas corresponding to the recording spots to rise. Thus, the sub-heating light applied before or after the writing light contributes to increasing the temperature of the areas corresponding to the recording spots. As a result, the temperature of the areas of the toner layer corresponding to the recording spots becomes higher than a threshold and those areas are transferred to the image-receiving layer to a record image on the image-receiving sheet.
The distance between the heating spot and each of the recording spots is preferably not more than 200 xcexcm downstream in a recording direction of main scanning in a preheating mode where the sub-heating light is applied prior to the writing light.
In this recording apparatus, the distance between the writing light and the sub-heating light in the main scanning direction in a preheating mode, or the distance between a recording spot and the heating spot, is limited not to exceed a predetermined value; hence, the loss of heat due to heat conduction is limited not to exceed a predetermined value, with the result that the heat of the sub-heating light is effectively used to contribute to heating the recording spots. The distance at which the contributory effect of heat is appreciable is not more than 200 xcexcm, preferably not more than 100 xcexcm.
Moreover, an emitting position of the writing light is preferably coincident with an emitting position of the sub-heating light in the main scanning direction.
In this recording apparatus, the emitting position of the writing light is coincident with the emitting position of the sub-heating light in the main scanning direction; hence, the loss of heat due to heat conduction is limited not to exceed a predetermined value, with the result that the heat of the sub-heating light is effectively used to contribute to heating the recording spots.
Further, the distance between the heating spot and each of the recording spots is preferably not more than 100 xcexcm upstream in a recording direction of main scanning in a post-heating mode where the sub-heating light is applied after the writing light.
In this recording apparatus, the distance between the writing light and the sub-heating light in the main scanning direction in a preheating mode, or the distance between a recording spot and the heating spot, is limited not to exceed a predetermined value; hence, the loss of heat due to heat conduction is limited not to exceed a predetermined value, with the result that the heat of the sub-heating light is effectively used to contribute to heating the recording spots. The distance at which the contributory effect of heat is appreciable is not more than 100 xcexcm, preferably not more than 50 xcexcm.
Further preferably, a time difference between the writing light and the sub-heating light is not more than 20 xcexcs in a preheating mode where the sub-heating light is applied prior to the writing light.
In this recording apparatus, the difference between the time when the heating spot by the sub-heating light was applied and the time when a recording spot by the writing light is applied in a preheating mode is limited not to exceed a predetermined value; hence, the loss of heat due to heat dissipation from the recording medium is limited not to exceed a predetermined value, with the result that the heat of the sub-heating light is effectively used to contribute to heating the recording spots. The time difference at which the contributory effect of heat is appreciable is not more than 20 xcexcs, preferably not more than 10 xcexcs.
Moreover, the time difference between the writing light and the sub-heating light is preferably not more than 10 xcexcs in a post-heating mode where the sub-heating light is applied after the writing light.
In this recording apparatus, the difference between the time when a recording spot by the writing light is applied and the time when the heating spot by the sub-heating light was applied in a post-heating mode is limited not to exceed a predetermined value; hence, the loss of heat due to heat dissipation from the recording medium is limited not to exceed a predetermined value, with the result that the heat of the sub-heating light is effectively used to contribute to heating the recording spots. The time difference at which the contributory effect of heat is appreciable is not more than 10 xcexcs, preferably not more than 5 xcexcs.
The recording method according to the present invention is characterized by applying writing light and sub-heating light to a medium for recording in a heated mode using the above-mentioned recording apparatus.
This recording method uses a recording apparatus that applies the heating spot to the recording medium at equal distances from the recording spots in the main scanning direction. Since all recording spots are heated in the same state, recording of an image can be accomplished with the individual recording spots exhibiting uniform recording characteristics even if they are arranged over a wide area.